1. Field of the Invention
The present invention relates to an OPC process, and more particularly, to an OPC method for a dual damascene structure.
2. Description of the Prior Art
In semiconductor manufacturing processes, in order to transfer an integrated circuit layout onto a semiconductor wafer, the integrated circuit layout is first designed and formed as a photo-mask pattern. The photo-mask pattern is then proportionally transferred to a photoresist layer positioned on the semiconductor wafer.
In recent years, with the increasing miniaturization of semiconductor devices, the design rule of line width and space between lines or devices becomes finer. However, the width is subject to optical characteristics. To obtain fine-sized devices in the exposure, the interval between transparent regions in a mask is scaled down with device size. When the light passes through the mask, diffraction occurs and reduces resolution. Moreover, when light passes through the transparent regions of a mask having different interval sizes, the light through the regions having small interval sizes is influenced by the transparent regions having large interval sizes and results in deformation of the transfer pattern. Currently, a technical called “optical proximity correction (OPC)” is developed. The OPC method is to imitate the feature that light passes through the photo-mask and to further compensate the pattern of the mask to form the desired pattern after the exposure process.
In the conventional arts, the “dual damascene” process is wildly used to form a metal interconnection system which is consisted of metal lines and plugs. However, the OPC method used for forming the masks of the metal interconnection system is not well studied.